The present invention relates to an image display apparatus which is retained on the observer's head. More particularly, the present invention relates to a headmounted display apparatus having a magnification varying function.
In a conventional head-mounted display apparatus, an image formed by an image display device is projected on an observer's eyeball at an initially set angle of view, as described in Japanese Patent Application Laid-Open (KOKAI) No. 03-188777 (1991). However, when the angle of view is fixed as in the conventional apparatus, various problems may arise according to the kind of image for observation. That is, when the angle of view is set relatively wide, as shown in FIG. 11(a), the magnification becomes high. However, an image seen at such a wide angle of view makes the observer feel a sensation of pressure and causes him or her to feel easily fatigued when observing such an image for a long time. In addition, since the pixels of the image display device are enlarged at a high magnification, curved lines of the displayed image are seen as uneven lines of pixels, as illustrated in FIG. 11(a). When the angle of view is set relatively narrow, as shown in FIG. 11(b), the image frame becomes small, so that the displayed image lacks force, and an image composed of fine lines becomes invisible.
In the conventional head-mounted display apparatus having a fixed angle of view, if an image according to NTSC, which has an aspect ratio of 4:3, is changed over to an image according to HDTV, which has an aspect ratio of 16:9, as described, for example, in Japanese Patent Application Laid-Open (KOKAI) No. 04-177986 (1992), the top and bottom of the image frame are cut, which makes the observer feel the images reduced in force.